This invention relates to an improved apparatus for producing spirally formed pipe, particularly spiral pipes having a diameter of approximately one inch or less.
A large potential for small diameter spiral pipes exists in the filter market, such as automobile oil filters. These filters typically have a perforated inner metal cylinder that is approximately one inch in diameter. Because pipes such as those used in oil filters need to be accurately and cleanly cut in large quantities, a pipe forming and cutting apparatus capable of fast and accurate cuts is necessary.
There are several known ways to form and cut a pipe. A pipe may be formed by spirally or helically winding a continuous strip of metal, and joining adjacent edges of the wound strip to form a spiral lockseam in the pipe. In some pipe forming and cutting machines, the spirally formed pipe is cut by moving a knife outside the pipe into an overlapping position with a knife inside the pipe. Other types of spiral pipe forming and cutting machines use multiple knives or rotate the knives around the pipe to cut the pipe into sections.
The accuracy of a cut depends upon minimizing the deflection of the pipe when the cutting knife or knives are engaged. In some pipe forming and cutting machines, the pipe may be supported by one or more rollers, opposite the outside knife, to counteract the force of the knives engaging in a cut. The support roller may be pneumatically or hydraulically driven to move the roller into and out of a support position.
Support rollers, while providing support against deflection in the direction of the force of the cutting knife, do not provide support for lateral deflection of a pipe during the cutting process. Rollers tend to require numerous parts as well as pneumatic or hydraulic systems that may be both costly and bulky. Furthermore, the pipe cutting process may be slower and less accurate than desired due to the time necessary to move the support rollers into a supporting position against a pipe. Accordingly, a pipe forming and cutting machine is necessary with improved lateral pipe support while cutting and that is both faster and more accurate.